Circuit interrupters



Oct. 8, 1957 H. J. LINGAL ET AL 2,809,252

CIRCUIT INTERRUPTERS Filed May 23 1955 2 Sheets-Sheet 2 United StatesPatent CIRCUIT INTERRUPTERS Harry J. Lingal, Penn Township, AlleghenyCounty, and Jerome Sandin and Richard Hauser, Forest Hills, Pa.assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania Application May 23, 1955, Serial No. 510,094

Claims. (Cl. 200-108) This invention relates to circuit interruptersand, more particularly, to circuit interrupters of the type used tocontrol light to moderate power distribution circuits.

An object of the invention is to provide a circuit interrupter embodyinga novel time delay trip device of the fluid dashpot type whereinseparate magnetic circuits are provided for operating the time delay andfor controlling the operation of the time delay.

Another object of the invention is to provide a circuit interrupterembodying a time delay device of the fluid dashpot type whereindifferent amounts of time delay are provided by operation of one or morecontrol valves to admit fluid to the dashpot at difierent rates,separate electromagnets being provided for operating the time delay andthe control valve.

Another object of the invention is to provide a circuit interrupterembodying a trip device having a fluid dashpot time delay device inwhich separate magnetic means is provided for operating the time delaydevice and for controlling the operation of the time delay device, eachof said separate magnetic means surrounding the main circuit through theinterrupter to provide a single turn energizing coil.

Another object of the invention is to provide a circuit interrupterembodying a trip device having time delay means, means for controllingthe time delay means, and electromagnetic means for actuating the timedelay means and the control means, the magnetic circuits for saidelectromagnetic means being separate to provide improved calibration ofthe trip device.

The invention, both as to structure and operation, together withadditional objects and advantages thereof, will be best understood fromthe following detailed description thereof when read in conjunction withthe accompanying drawing.

In said drawing:

Figure 1 is a vertical sectional view taken through the center pole of athree-pole circuit interrupter embodying the principles of theinvention.

Fig. 2 is an enlarged sectional view through the trip device for one ofthe poles of the interrupter.

Fig. 3 is a sectional view of a portion of the time delay device shownin Fig. 2, showing the short time delay control means.

Referring to Fig. l of the drawing, the circuit interrupter includes aplurality of pole units, each comprising a separable contact structureindicated generally at 11, and an overcurrent trip device indicatedgenerally at 13. The contact structure and trip device for each pole ofthe circuit interrupter are mounted on separate insulating bases 15which are rigidly secured to a metal panel 17 by means of screws 19.Since the pole units are alike, only one will be described herein.

The contact structure comprises stationary main contacts 23 and astationary arcing contact 25 all supported on the inner end of aU-shaped terminal conductor 27 (Fig. 1), the legs of which extendthrough suitable open- Patented Oct. 8, 1957 ICC . ings in the base 15and panel 17. Cooperating with the stationary main contacts 23 and thestationary arcing contact 25, respectively, are movable main contacts 29and a movable arcing contact 31. The movable main contacts 29 arerigidly mounted on a channel-shaped main switch arm 33 pivotally mountedat its lower end on a pin 35 supported in a bracket 37 which is rigidlymounted by means of bolts 39 (only one being shown) on a lower U-shapedterminal conductor 41. The movable arcing contact 31 is mounted on acontact carrying member 43 rigidly mounted on the upper or free end ofan arcing contact arm 47 which is also pivoted on the pin 35. A flexibleconductor 49 has its upper end secured to the movable arcing contact andits lower end secured to the upper end of the main contact arm 33.

The main stationary contacts 23 (Fig. 2) are pivotally supported inbearing openings in an extension 55 of the terminal 27, and are biasedby means of a common spring 57 into engagement with the movable maincontacts 29 in the closed position of the circuit interrupter. Thestationary arcing contact 25 is pivotally supported on a bracket 60secured to the terminal extension 55, and is biased by means of a spring64 into engagement with the movable arcing contact 31.

The movable contact structure is normally maintained in the closedposition by an operating mechanism indicated generally at 61 (Fig. I)mounted in a U-shaped frame 63. The frame 63 comprises spaced sidemembers 65 and a connecting cross member 67 and is supported on aplatform 69 which forms a cross member of a main bracket comprising apair of spaced side members 71 joined at their outer ends by the crossmember or platform 69. The platform extends substantially across thewidth of the circuit interrupter, and the side members 71 are rigidlysecured to the panel 17 on the outer sides of the two outer pole units.

The operating mechanism includes a lever 73 pivotally mounted on a pivotpin 75 supported in the side members 65 of the frame 63. The lever 73comprises a pair of spaced levers rigidly joined by an angle member 77which extends across all of the poles of the interrupter. The anglemember 77 is operatively connected to the main movable switch arm 33 bymeans of an insulating connecting member 81 and a pivot pin 79 in themain switch arm. The other end of the connecting member 81 is pivotallyconnected to the angle members 77 by means of a pivot pin and a bracket82 rigid with the angle member 77. There is a connecting member 81 foreach pole of the circuit interrupter connecting the angle members 77 tothe main moving contact member 33 for each pole unit so that, uponoperation of the lever 73, the movable contact structure for all thesepoles move in unison.

An operating linkage comprising toggle links 83, 85 and 87 is providedto hold the lever 73 and, consequently, the movable contacts in theclosed position and to operate the movable contacts to open and closedpositions. The toggle link 83 is pivotally connected to lever 73 by apivot pin 89, and the toggle link 85 is connected by a knee pivot pin 91to the toggle link 83 and by a knee pivot pin 93 to the toggle link 87.The toggle link 8; is pivotally mounted on a fixed pivot 97 in the frame6 mally slightly underset above a line drawn through the centers of thepivot pins 89, 93 and the closing toggle 85, 87 is normally slightlyunderset below a line drawn through the centers of the pivot pins 91,97.

.The tripping toggle 83, 85 is normally biased in a'" 3 direction tocause its collapse by components of the springs 57 and 64 and springs'98 (only one being shown) which bias the moving main contact structurefor the severalpoles of the interrupter in opening direction and biasthe connecting members 81 toward' the lefttFig. 1). The tripping toggle83, 85 is normallyprevented'from collapsing by means of a main' latchmember 99 pivoted on a pin'100 and connected by a link 101 to the kneepin 91 of the tripping toggle, the link 101 being connected to the latchmember 99 by a pin 103.

The main latch'99 is'held in latching position by an intermediate latchlever 1'05 pivoted on a'pin'107 in' the frame 63. The latch lever 1'car'ries a latch roller 111 which normally engages'themain'latch 99 toreleasably hold the latter 'in'holding position. The latchlever'I05 atits lower end carries 'a latch'member 113 which normally engages alatchmember 115 on a light-load latch member'117' pivoted on a 'pin'119in the frame-63. The latch lever 105 and the member 117 are 'bias'ed'totheir latching positions by a spring 121'tensioned between the parts.Rigidly mounted on the right hand end of member11'7 is a trip bar 123which extends across all of the poles of the-interrupter and has securedthereto an insulating bracket-125 (Figs. 1 and 2) for each pole of theinterrupter cooperating with the trip'device 13forthe corresponding poleunit.

As long as the main latch 99 is held in'latching' position by thelatching mechanism just described, the tripping toggle 83, 85 will,through the link 101, be held in the position shown in which theinterrupter contacts are held in closed position. The closing'toggle85,'87 is normally prevented from collapsing by a shouldered support member131 pivoted on the pin 107 and biased bya spring 133 into supportingengagement with the knee pin 93 of the closing toggle.

The circuit interrupter is tripped open by operation of the trip device13, to be described later, for any pole of the interrupter. Operation ofthe trip device actuates the trip bar 123 to effect release of the latchlever 105 which, in turn, releases the main latch 99. When the mainlatch 99 is released, the force of the springs 57 and 98 biasing themain movable switch arm 33in opening direction and which is transmittedthrough the connecting members 81 to the lever 73, causes-the trippingtoggle 83, 85 to collapse upwardly and effects opening movement ofthe-movable main switch arms 33 for a'll of the poles. of the breaker.

The closing toggle 85, 87 does not immediately collapse followingrelease of the latchmechariism, since it is held by thesupport member13. During the unlatching movement of the main latch 99, a cam (notshown) thereon engages the tail of the support member '133 and movesthis member in a clockwise direction about its'piv- 0t 107 to disengagethe shoulder thereon from beneath the pin 93, whereupon theclosingtoggle 85, 87,being no longer supported, collapses downwardlyunder its own weight and the weight of the moving armature of theclosing solenoid which will be described later. Collapse of the closingtoggle 85, 87 causes the tripping toggle 83, 85 to be reset to thrusttransmitting position and also effects resetting of the latch mechanismto'latching position. The operating mechanism is now in condition for aclosing operation.

Means is provided to hold the movable arcing contact arm 47 stationarywith full contact pressure until the movablemain contacts have separateda predetermined distance from the stationary main contacts. This meanscomprises a cam member 135 (Figs. land 3) rigidly securedto themovingarcing contact arm 47. Cooperating with a .cam surface 137 on the cammember- 135 is a roller 139. rotatable on'thepin80 whichpivotallyconnects the lever 73 to the connecting member 81. .-It will beremembered that the connecting member 81 is connected by the pin 79 tothe moving main contact arm 33. .Inorder to openthe contacts the lever73 moves in a counterclockwise direction about the pivot moving theroller along the cam surface 137. The configuration of the cam surface137 is such that during the early part of the opening movement and untilthe roller 139 reaches a point A on the cam member 135, the roller 139holds the cam member and, hence,-the movable arcing contact arm 47stationary in'thefully closed position. During this early movement, thecounterclockwise movement of the lever 73 and the leftward movement ofthe connecting'member 81 moves the moving main contact arm 33 in openingdirection until the pin 79 engages the arcing contact arm 47. At thistime, the roller 139 is at the point A. Thereafter, during the openingmovement it moves along an arcuate surface'141 of the cam member which,it will be noted, is struck around the center of the pin 79 with the pinin contact with the arcing contact arm 47 By this means, the two movingcontact arms 33 and 47 are locked together for unitary movement duringthe rest of the opening operation.

During opening and closing operations and in the closed position, goodelectrical contact is provided at the pivoted end of themovable maincontact arm 33 by means of spring biased contact members 143 (Figs. 1and 2)which arepivoted on the bracket 37 adjacent the terminal conductor41 and biased into engagement with opposed arcuate surfaces 145 'on thecontact arm 33 by a spring 147.

The main current path through the interrupter is from the upper'terminal27,'through the main stationary contacts 23, the main moving contacts29, the main contact arm "33 and'through the contact members 143 to thelower terminal 41. A parallel current path is formed from the upperterminal 27 through the stationary arcing contact 25, the'moving arcingcontact 31, through the flexible conductor 49, the main moving contactarm 33 and the contact members 143 to the lower terminal '41. Themagnetic effect of the current loop through the arcing contacts in theclosed contact position tends to blow the arcing contacts on, thuspermitting the interrupter to carry its rated interrupting current forthe duration of the short time delay provided by the short time delaymeans of the trip device13.

The circuit interrupter is closed automatically by energiz-ation of aclosing solenoid 149 (Fig. l) which is effected either manually or byautomatic means. The closing solenoid '149 comprises a fixed'magnetyoke'151 and a fixedcore member 153 mounted on the underside of theplatform 69. A movable armature 155 is attached to the lowerend of anoperating rod 157 which extends upwardly and has its upper end pivotallyconnected to the knee pin 93 of the closing toggle 85, 87. An energizingcoil 159 is'supported on the lower end'of a supporting bracket 161having its upper end fastened to the platform 69.

In the closed position of the interrupter, the armature 187 is held initsraised position (Fig. 1). When the breaker is tripped open, theclosing toggle 85, 87 collapses downwardly permitting the armature 155to assume its lower or unattracted position. Thereafter, uponcnergization of the coil 159, the armature 155 is attracted upwardly andacts through the rod 157 to straighten the closing toggle 85, 87 andclose the contacts.

The action of the contact structure during a closing operation is thereverse of that of the opening operation.

The trip device 13 includes a tripping electromagnet indicated generallyat 163 (Figs. 1 and 2) and a time delay device indicated generally at165. The tripping magnet 163 comprises a U-shaped magnet yoke '167 (Fig.2) rigidly secured to the base '15 of its corresponding pole unit bymeans of bolts 169 (only one being shown). The legs 171 of the magnetyoke 167'extend downwardly on opposite sides of the main currentcarrying switch arm 33 and'terminate'in pole faces 173. Also mounted onthe'base IS by'means'ofthe bolts 169 and acne-zeobetween the legs 171 ofthe yoke 167 is a separate U- shaped magnet yoke 175, the legs 177 ofwhich extend toward the left (Fig. 2) on opposite sides of the mainmovable switch arm 33 and terminate in pole faces 179. The electromagnetcomprising the magnet yokes 167 and 175 is energized by the current flowin the switch arm 33, which forms a single turn energizing coil passingthrough the U of both of the magnet yokes. The legs 171 and 177respectively of the magnet yokes 167 and 175 are spaced from each other.

The time delay device 155 and the elements of the trip device, otherthan the magnet yokes, are supported in a U-shaped frame indicatedgenerally at 131 (Fig. 2). The frame 181 comprises spaced side members183 (only one being shown) integrally joined by a cross member 185. Thelower portion of each of the side members 183 are rigidly supported onthe base by means of a belt 187, and the upper end of each of the sidemembers 183 is rigidly secured to the adjacent downwardly extending leg171 of the magnet yoke 167 by means of a bolt 189 which threadedlyengages a bracket 191 riveted to the leg 171.

The trip device is actuated by a moving armature 193 mounted on a pairof spaced arms 195 (only one being shown) joined by a cross member 197and pivotally supported on pins 199 in the side members 183. Uponenergization of the electromagnet in response to overcurrents, thearmature 193 is attracted to the pole faces 17 3 and actuates a trip rod201 to effect tripping of the interrupter. The trip rod 201 engages aroller 203 mounted on one end of a bell-crank lever 205 pivoted on a pinsupported in the frame 181 and rotates the lever 205 counterclockwise.During this movement of the bell crank 205, the other end thereofengages a pin 207 in one end of a bell crank 208 and rotates the latterin a clockwise direction. The bell crank 208 is mounted on a pin 209 inthe frame 181 and, when actuated, the other end 210 thereof engages ascrew 211 threaded into the bracket 125 (Figs. 1 and 2), and actuatesthe previously described trip 123 and the latch mechanism to trip theinterrupter.

The trip rod 201 is moved upwardly to trip the interrupter under thecontrol of the time delay device 165 which comprises, enerally, aflexible diaphragm 213 (Fig. 2) attached to the lower end of the triprod and valve elements for controlling the admission of air to the spacebelow the diaphragm at various rates to provide difi'erent amounts oftime delay. The flexible diaphragm 213 is disposed in a chamber 215formed in an upper housing member 217 and a lower housing member 219,both of the housing members being of molded insulating material. Theouter edge of the diaphragm 213 is clamped between the housing members217 and 219, together with a sealing gasket 221 to form an airtightseal. The housing members are secured together and rigidly secured to across member 222 of the frame 181 by means of bolts 223 (Figs. 1 and 2).The central portion of the diaphragm 213 is suitably clamped betweenupper and lower clamp members 225 and 227, respectively, to form anair-tight seal. The clamp members are rigidly secured to the lower endof the trip rod 201. Disposed above the upper clamp member 225 andsurrounding the trip rod 201 is a cylindrical member 229 having spacedflanges 231 at its upper end between them forming an annular groove 233which is engaged by opposed ears 228 (only one being shown) on the crossmember 197 of the armature lever 195. The cylindrical member 229 has abore 230 therein in the upper end of which is disposed a collar 232fastened to the trip rod 201. A coil spring 234 is disposed in thecylinder bore 230 and is compressed betweeen the collar 232 and thebottom of the bore 230.

Since the spaces above and below the diaphragm 213 are completely sealedoff from each other and the space above the is at atmospheric pressure,any

6 force tending to raise the trip rod 201 will be restrained by thepartial vacuum below the diaphragm. In order to control the rate oftripping movement of the trip rod 201, valve devices are provided toadmit air to the space below the diaphragm. The valve devices comprise along time delay valve indicated generally at 235 (Fig. 2), and a shorttime delay valve indicated generally at 237 (Fig. 3

The long time delay device will be described first. The central bottomportion of the lower housing memher 219 is molded to form a valve seat241 in the shape of an inverted truncated cone. Surrounding the valveseat 241 is a tubular metallic member 243 molded into the housing member219 and threaded internally to receive a valve 245 having a conicalopening therein for cooperating with the valve seat 241. The valve 245is provided with a flange 247 for supporting a knurled adjusting knob249 of molded insulating material which is biased thereagainst by aspring 251. An air passage 259 in the form of a groove is provided alongthe threaded portion of the valve 245, and a passage 261 is providedaxially through the valve seat 241. The flow of air into the chamberbelow the diaphragm is through a filter 257, the passage 259, theorifice defined by the valve 245 and the valve seat 241 and through thepassage 26]..

The inner surface of the knob 249 is provided with serrations whichengage corresponding serrations on the valve 245, whereby rotation ofthe knob 249 rotates the valve 245 which, due to its threaded engagementwith the fixed tubular members 243, moves the valve axially of the valveseat 241 to thereby vary the rate of admission of air to the space belowthe diaphragm 213 and, hence, varies the amount of time delay in theoperation of the trip device.

The valve device 235 is calibrated by pushing upwardly on the knob 249to disengage it from the valve member 245. The knob 249 is then set tozero and the valve member 245 rotated to the closed position.Thereafter, the knob 249 is released and restored to engagement with thevalve by the spring 251. The knob 249, together with the valve 245 isthen rotated to the position to provide the required amount of timedelay.

The short time delay valve device 237 (Fig. 3) controls a passage foradmitting air from the chamber 215 above the diaphragm 213 to the spacebelow the diaphragm at a rate to provide tripping with a very short timedelay in the order of alternating current cycles. The valve device 237comprises a tubular valve element 273 (Fig. 3) disposed in an opening275 in the upper housing member 217. The valve element 273 is providedwith an enlarged head portion 277 seated in an opening 279 in the bottomhousing member 219. The valve element is also provided with a valve 281,slidably disposed in the tubular valve element 273, and which normallycooperates with a valve seat to close a communication with the oppositesides of the diaphragm 213. The valve element 273 is provided with anaxial passage in which is disposed a tapered projection 285 of the valve281 and which is normally closed by the valve 281. The head 277 of thevalve element 273 is provided with horizontal passages 287. A passage289 in the housing member 217 communicates the chamber 215 above thediaphragm 213 to the opening 275 above the valve seat, and a passage 291in the housing member 219 communicates the chamber 215 below thediaphragm 213 with the passages 287.

It will be seen that upward movement of the valve 281 will open thepassage comprising the passages 289, 287, and 291 and establish acommunication from the upper side to the lower side of the diaphragm.

The valve 281 (Fig. 3) is actuated to the open position by means of anarmature 292 (Fig. 2) rigidly mounted on one end of a lever 293 which ispivoted on the pin 209. The other end of the lever 293 is connected by alink 294 to a lever 295 pivotally mounted at 296 on the housing 217. Thelink 294 is guided in its movement by a pin 297 and slot 298 and has apin and slot connection 299-30i9 with a bracket 301 rigidly mounted onthe lever 295. A bracket 393 (Fig. 3) secured to the lever 295 engagesin a notch 305 in the upper end of the valve 231, so that upon actuationof the lever 295 by the armature 292 acting through the lever 293 andlink 294, the valve 281 is moved upwardly to the open position. Thisopens the previously described communication permitting air to pass fromthe chamber 215 above the diaphragm 213 to the space below the diaphragmto control the rate of tripping movement of the trip rod 201.

The amount of opening of the valve and, hence, the rate of flow of airto the space below the diaphragm is controlled by an adjustable S-shapedstop member 337 (Fig. 3). The upper portion of the stop member 307 isdisposed in the path of tripping movement of the upturned end of thelever 295 to be engaged thereby and thus limit the extent of opening ofthe valve 281.

The stop member is adjustable to vary the amount of short time delay bymeans of an adjusting screw 3 59 which threadedly engages the centercross bar 311 of the S-shaped member 307. The adjusting screw 309 isrotatably mounted in an insulating cross bar 313 supported on theunderside of the housing member 217 by means of screws 315 only one ofwhich is shown. A knurled knob 317 is mounted on the lower end of thescrew 309 below the cross bar 313, whereby the adjusting screw 309 maybe rotated to provide the proper setting of the stop 367.

A portion 319 of the screw 309 also engages a pointer 321, one end ofwhich projects outward through a slot in a scale plate 323 to give anindication of the setting of the adjustable stop 307 for the short timedelay valve 281.

The pick-up point; that is, the magnitude of overload current requiredto actuate the armatures 193 and 292 (Fig. 2) may be varied by varyingthe tension respectively, of springs 325 and 327. The spring 325 has oneend attached to a yoke 329 which has its legs pivotally supported inspaced grooved studs 331 (only one being shown) supported in the housingmember 217. The right-hand end of the yoke 329 is provided with inwardlyextending projections 333 which engage in an annular groove 335 in thecylindrical member 229. The other end of the spring 325 is attached to apointer 337 which is threadedly engaged by an adjusting screw 339rotatably mounted in the cross bar 313 and which is provided with anadjusting knob 341 on the end thereof below the cross bar. Rotation ofthe screw 339 varies the tension of the spring 325 to thereby vary thepick-up point of the armature 193. The tension of the spring 327 for thearmature 292 is similarly adjusted by means of a screw and pointer (notshown) but which are like the adjusting means for the spring 325.

The legs of the magnetic yokes 167 and 175 are spaced from each other inorder that operation of armature 193, upon energization of its magnetyoke 167, will not shunt part of the flux from the magnet yoke 175 aswould be the case if the yokes 167 and 175 formed a single magnet yoke.This prevents disturbing the calibration of the short time delayarmature 292 when the armature 193 is attracted to its pole faces 173.

The trip device functions with time delays of different durations inresponse to overload currents of different magnitudes. For instance, thedevice may function with a relatively long time delay in the order ofseconds, in response to overload currents up to approximately ten timesnormal rated current and with a relative short time delay in the orderof alternating current cycles.

Assuming an overload current flow ten times normal rated current, thetripping electromagnet becomes enerev gized by the current flow throughthe switch arm 33 sufficiently to attract the armature 193 upwardly. Thearmature 193 acts through the lever 195, cylindrical member 2-29, andthe spring 234 to produce an upward thrust on the trip rod 201, themovement of the trip rod being retarded by the partial vacuum below thediaphragm 213. The trip rod 201 moves slowly upwardly in trippingdirection as air is drawn into the space below the diaphragm through thelong time delay valve 235. The slow upward movement of the trip rod 201acts through the roller 203 to slowly rotate the bell crank -35 in acounterclockwise direction. The upper end of the bell crank 205 actsthrough the pin 207 to rotate the bell crank 208 in a clockwisedirection until eventually the end 210 of the bell crank 238 engages thescrew 211 and actuates the trip bar 123 and eifects release of the latchmechanism and opening of the interrupter in the previously describedmanner.

As soon as the interrupter contacts have opened the trippingelectromagnet is deenergized and the armature 193, the cylindricalmember 229, and the trip rod 201 are restored to their normal positionsby the spring 325. A spring biased reset or bypass valve 343 (Fig. 2)controls a passage through the diaphragm 213 to provide quick dumping ofthe air in the space below the diaphragm and quick restoration of theparts.

Energization of the electromagnet in response to overload currents aboveten times normal rated current attracts the short time delay armature292 which acts through the link 294 to move the lever 295 upwardlyagainst the stop 307 opening the short time delay valve 237 an amountdetermined by the adjustment of the stop 307. This admits air to thespace below the diaphragm 213 at a higher rate than the long time delayvalve 235 alone and provides a short time delay in the order of cyclesin the tripping operation of the device.

The trip device may be arranged to trip the interrupter after arelatively long time delay and instantaneously by omitting the shorttime delay valve 237 and omitting the slot 345 in the lever 293 whichcarries the armature 292, as shown in Fig. 1. The armature 292 inresponse to an overload current above a predetermined value will actthrough the pin 207 to instantaneously trip the interrupter.

The invention provides a trip device for a circuit interrupter having atime delay device and control means for the time delay device in whichthe electromagnetic means for operating the time delay device and thecontrol means therefor are separate to prevent disturbing thecalibration of one electromagnet upon operation of the otherelectromagnet. The magnet yokes of each of the electromagnets surroundthe main current carrying path through the interrupter to provide singletime energizing coils for the electromagnets.

Having described the invention in accordance with the provisions of thepatent statutes, it is to be understood that various changes andmodifications may be made in the structural details and combinations ofelements disclosed without departing from the spirit of the invention.

We claim as our invention:

1. In a circuit interrupter having a main current carrying circuittherethrough, an electromagnetic trip device comprising a fixed magnetyoke surrounding said main current circuit to be energized by currentstherein, a trip rod operable to effect automatic operation of saidinterrupter, an armature operable by energization of said magnet yoke inresponse to overload currents of certain value to positively actuatesaid trip rod, time delay means retarding tripping movement of said triprod comprising a fluid dashpot connected to said trip rod, a pluralityof valve means admitting fluid to said dashpot at different rates,separate electromagnetic means operable in response to overload currentsof certain other value to positively operate one of said valve means toincrease the rate of admission of fluid to said dashpot, said separateelectromagnetic means comprising a separate fixed magnet yokesurrounding said main current carrying circuit and an armature connectedto operate said one valve means.

2. in a circuit interrupter having a main current path therethrough, atripping electromagnet comprising a fixed U-shaped magnet yoke, saidmain current path extending through said magnet yoke to form a singleturn energizing coil, a tripod movable to effect automatic operation ofsaid interrupter, an armature operable by energization of saidelectromagnet in response to certain overload currents to positivelyactuate said trip rod, time delay means retarding tripping movement ofsaid trip rod, a plurality of valve means admitting fluid to saiddishpot at different rates, a second electromagnet operable in responseto certain other overload currents in said main circuit to positivelyoperate one of said valve means to increase the rate of admission offluid to said dashpot, said second electromagnet comprising a U-shapedyoke through which the main circuit extends to form a single turnenergizing coil and an armature connected to operate said one valvemeans.

3. In a circuit interrupter having relatively movable contacts, a maincurrent path through said interrupter including said contacts, a tripmember operable to effect automatic opening of said contacts, a tripdevice com-- prising a magnetic circuit surrounding said main currentpath and including an armature operable in response to overload currentsto positively actuate said trip member, a time delay device retardingtripping operation of said trip member comprising a fluid dashpot, aplurality of valves admitting fluid to said dashpot at different rates,one of said valves being operable to increase the rate of admission offluid to said dashpot, and electromagnetic means comprising a separatemagnetic circuit surrounding said main current path and responsive toother overload currents, said separate magnetic circuit including anarmature movable to positively operate said one valve.

4. In a circuit interrupter having a main current path through saidinterrupter including relatively movable contact means, a trip memberoperable to effect automatic opening of said contact means, a time delaymeans effecting a time delay in the operation of said trip member, acontrol element for controlling said time delay means to effect apredetermined time delay in the operation of said trip member,electromagnetic means operable to actuate said trip member and saidcontrol element comprising separate magnetic circuits surrounding saidmain current path and responsive to overload currents of differentvalues, each of said magnetic circuits including an armature operated byenergization of said magnetic circuits in response to overload currentsof different values, one of said armatures being connected to positivelyactuate said trip member and the other of said armatures being connectedto positively actuate said control element.

5. In a circuit interrupter having a main current carrying circuitincluding a switch arm movable to open and closed positions, a tripmember operable to eflect automatic opening of said switch arm, timedelay means pro-- viding a time delay in the operation of said tripmember, a control element operable to decrease the time delay providedby said time delay means, electromagnetic means comprising separatemagnetic circuits surrounding said switch arm whereby said switch armprovides a single turn energizing coil for energizing said separatemagnetic circuits in response to overload currents of different values,each of said magnetic circuits including a movable armature, one of saidarmatures being operable when its magnetic circuit is energized inresponse to overload currents below a predetermined value to positivelyactuate said trip member, and the other of said armatures being operablewhen its magnetic circuit is energized in response to overload currentsabove said predetermined value to positively actuate said controlelement.

References Cited in the file of this patent UNITED STATES PATENTS754,505 Scott Mar. 15, 1904 2,000,442 Healis May 7, 1935 2,144,501Lingal Jan. 17, 1939 2,340,973 May et al Feb. 8, 1944 2,669,623 MacNeillet al Feb. 16, 1954 2,700,082 Lingal Jan. 18, 1955 FOREIGN PATENTS282,642 Great Britain Nov. 25, 1927

